Method of tensioning thread on a sewing machine

ABSTRACT

A tension balancer having a spring-biased indicator with appropriate indicia and means to attach to the thread of a sewing machine. The tension balancer permits the exact adjustment of the proper balance of tension between the needle thread and bobbin thread to provide a perfect stitch. The method of using the tension balancer requires the operator to attach the springbiased plunger in turn to either the bobbin thread or the needle thread and kinematically adjust the sewing machine to provide the appropriate dynamic tension.

United States Patent inventor Arthur E. Shryock 1415 Amelia Ave.,Findlay, Ohio 45840 867,1 19

Oct. 13, 1969 Nov. 9, 1971 Appl. No. Filed Patented METHOD OF TENSIONINGTHREAD ON A SEWING MACHINE 5 Claims, 5 Drawing Figs.

Int. Cl. D05b Field of Search 112/254,

i i i/i jj i/i/ li/i/ijgam //I I /7 y/ I [56] References Cited UNlTEDSTATES PATENTS 698,370 4/1902 Burrows 177/232 2,450,188 9/1948 DeGraaf177/232 X Primary Examiner-Jordan Franklin Assistant ExaminerGeorge H.Krizmanich Attorney-Sughrue, Rothwell, Mion, Zinn & MacPeak ABSTRACT: Atension balancer having a spring-biased indicator with appropriateindicia and means to attach to the thread of a sewing machine. Thetension balancer permits the exact adjustment of the proper balance oftension between the needle thread and bobbin thread to provide a perfectstitch. The method of using the tension balancer requires the operatorto attach the spring-biased plunger in turn to either the bobbin threador the needle thread and kinematically adjust the sewing machine toprovide the appropriate dynamic tension.

PATENTEUHUV 9197i 3,618,541

"'IIIII AWIIIIIIIIIAW ATTORNEYS METHOD OF TENSIONING THREAD ON A SEWINGMACHINE BACKGROUND OF THE INVENTION l Field of the Invention Thisinvention relates to an apparatus and method of providing the properbalance of tension between the needle thread and bobbin thread in asewing machine to provide a correct stitch pattern.

2. Description of the Prior Art A sewing machine is basically designedto interconnect or lock two separate threads on opposite sides of apiece of fabric or fabrics. This is accomplished by repetitively forcingan upper or needle thread through the fabric and then inserting a loweror bobbin thread through the upper thread to form a closed seriesofloops. The desired perfect stitch will have its threads locked betweenthe two layers of fabric without any surplus loops on the top or bottomof the material. If the upper thread is too tight relative to the lowerthread, the thread will merely lie across the top of the fabric or evenbreak if the tension is beyond its limits of strength. Likewise, if thebobbin or lower thread is too tight, it is also susceptible to breakageand will lie across the bottom of the fabric exposing the loop portionof the upper thread. An improper tension balance can produce irregularstitches, a puckering of the material, skipped stitches, and brokenupper and lower threads.

The prior art has sought to incorporate in the sewing machine meansforadjusting the tension of both the needle thread and bobbin thread. Thenormal sewing machine generally has a dial or knob that is insertedbetween the spool thread and the needle and permits the looping of aportion of the thread through a spring member to vary the threadtension. The lower thread or bobbin thread also utilizes a tensionspring on the bobbin that can be adjusted by a screwdriver. The actualadjustment of the sewing machine to provide properly locking stitches isa procedure of trial and error and generally requires a mercerizedthread because synthetic threads will normally not break under hightension. The operator will generally set the upper thread tensionbalance and experimentally make a line of stitching. He then is requiredto inspect the fabric and the stitch, and if he finds that the seam ispuckered, he will know that both tensions are too tight. If he observesthat the bottom thread is looped, he will know that the upper threadtension needs to be tightened while, if the top thread lies on the topof the fabric, he will know that he must loosen the upper threadtension. The operator, if the stitching fails on any of the above visualinspections, will be forced to repeat his experiment and continuallyperform minute adjustments until he has produced a perfect stitch.

The sewing machine operator generally approached the adjustment of hismachine by loosening the bobbin thread tension and lowering the dialsetting of the needle tension since this will permit him to at leastknow the direction of adjustment, that is a gradual tightening of thetension during his experimentation. It has also been recommended in theprior art that the stitching itself be grasped and pulled evenly andfirmly apart until one or both the threads break. This test isfor thepurpose of demonstrating the balancing of the tensions between theneedle thread and bobbin thread. If both the threads break then thetensions are appropriately balanced. However, if neither thread breaks,the tensions are too loose while if only one of the threads breaks it isindicative of an improper tension balance.

While sewing machines contain the basic elements for effecting anadjusting of the tension balance between the upper or needle thread andthe lower or bobbin thread, it is very obvious that the repetitiveexperimental approach is highly unsatisfactory in time and result. Thisapproach has been found to be highly exasperating to the averagehousewife and further costly and time-consuming in the commercialenvironment.

SUMMARY OF THE INVENTION The present invention provides both theapparatus and method to overcome the problems of the prior art in asimple and efficient manner.

This is accomplished by providing a separate tension balancer that willpermit the independent and exact adjustment of both the upper or needlethread and the lower or bobbin thread to provide a perfect stitch. Withthe use of the apparatus of this disclosure, the upper or needle threadcan be quickly and efficiently determined by applying a dynamic tensionto the thread and simply dialing the appropriate tension in correlationwith the indicia of the tension balancer. Likewise, the lower or bobbinthread can be adjusted by again applying a dynamic tension to the bobbinthread while making appropriate adjustments of the tension screw incorrelation with the indicia of the tension balancer.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a segmentary elevationalview in cross section showing the device of this invention.

FIG. 2 is a side-elevational view of the tension balancer adjusting thetension on the top thread of the sewing machine.

FIG. 3 is a side-elevational view of the tension balancer adjusting thetension of the bobbin thread.

FIG. 4 is a perspective view of a bobbin case.

F IG. 5 is a cross-sectional view of a perfect stitch.

DESCRIPTION OF THE PREFERRED EMBODIMENT As illustrated in FIG. 1, thetension balancer l0 comprises a housing 20 which can be a shell of anygeometrical configuration. A tubular-shaped penlike configuration hasbeen found to be highly satisfactory. The housing 20 encloses a plunger14 which has a spring seat 16 at one end and a slot hook 18 to the otherend. The hook can assume other shapes as long as it provides anattachment point on the plunger 14. The plunger is appropriatelycalibrated and marked with indicia points A and B. Point A correspondsto the appropriate tension point of the needle thread while point Bcorresponds to the appropriate tension point of the bobbin thread. Aclosure member 22 provides the other seat for the spring music wire 12and establishes the precompression of the spring assembly. Music wirehaving a spring constant value of approximately 9.4 oz. per 1 inch hasbeen found to be highly successful. The indicia marks are spaced on theplunger to produce a needle thread tension of approximately 152.5 gramsor 5.38 02. at point A and a bobbin thread tension of approximately 69grams or 2.44 02. at point B. This produces a differential of tension ofapproximately 83.3 grams or 2.94 oz. of tension between the needlethread and the bobbin thread. Actual experiments have shown that it ispossible to produce adequate stitches with a plus or minus variation of10 grams on both the needle and bobbin thread tensions. A cap 24 havinga clip 26 has proven to be a convenient modification of the tensionbalancer. The cap is either snapped or screwed upon the housing 20.

FIG. 5 discloses a perfect stitch configuration where the needle thread28 is interlocked in the center of the material with the bobbin thread30. The method of adjusting the sewing machine to produce the idealstitch, shown in FIG. 5, is the independent adjustment of the upper orneedle thread and the lower or bobbin thread by the tension balancer ofthis invention. The sequence of adjusting, that is the upper thread orthe lower thread, is unimportant since either could be adjusted first.To adjust the needle thread, the sewing machine should be threaded as innormal use with the thread passing from the spool through the upperthread guide and through the upper thread tension control 32 to thethread takeup lever 34. After the thread passes through the threadtakeup lever 34, it is attached to the end of the tension balancerplunger 14 through appropriate grip means. The grip means can actuallygrip onto the thread or, as shown in the simplified embodimentillustrated,'can consist of'aa hook or notch' l8which permitsa loopportion of the thread to be gripped. The pressure foot lever 36 is thenlowered into its operative position to place the needle thread 28 intension. The thread is then gently pulled by the tension balancer withthe end of the plunger 14 preferably pointed towards the takeup lever34. During this pulling motion, the upper thread tension control isadjusted to cause the plunger indicia A to appear at the end of thetension balancer housing. When the indicia A remains steady while thethread is being pulled, the needle thread tension is correct. Thisdynamic tension is effectively established in one calibration. Thethread should slide easily through the adjustment plate of the tensioncontrol throughout the entire calibration. If the pressure of the threadagainst the plunger 14 is not sufficient to force the plunger 14 toextended to the calibration point A, the tension on the thread 28 mustthen be increased to create sufficient pressure to allow the plunger toextend through the calibration point A. If the tension on the thread issuch that the plunger is allowed to extend beyond the calibration pointA, tension on the needle thread is too great and therefore the tensionmust be readjusted by easing the adjustment of the tension control 32 tothe point where the thread will slide easily through the adjustmentplate while the plunger 14 on the tension balancer 10 remains fixed atthe calibration point A.

In adjusting the bobbin tension, the bobbin is inserted into the bobbincase as illustrated in FIG. 4, and installed in the sewing machine inthe normal fashion. The bobbin thread 30 is pulled up through the throatplate 38 and an appropriate loop is fastened in the end of the threadand hooked in the notch hook 18 in the plunger 14. The thread is thenslowly pulled through the throat plate 38 with the end of the plunger 14pointing toward the hole in the throat plate 38. When the indicia mark Bremains steady at the end of the tension balancer housing, the bobbinthread tension is correct if the indicia point B is beyond the tensionbalancer housing, then the tension is too tight while, if it remainswithin the housing the tension is too loose, and the adjusting screw 42on the bobbin casin g 40 should be appropriately adjusted.

With appropriate modification, this device can be used to set propertensions on the threads of sewing machines for the most efficientoperation of the machine upon unusual materials or unusual stitches suchas zigzag stitching or other stitching which requires a measure oftension on the needle thread and bobbin thread to a different degreefrom normal materials and normal sewing methods. Upon completion of thespecial sewing, the operator of the sewing machine can immediatelyreturn the machine to its proper and normal adjustment by the use of thetension balancer 10 of this invention.

What is claimed is:

l. A method of tensioning a thread on a sewing machine by the use of acalibrated tension balancer having a resiliently bias plunger withindicia comprising the steps of:

attaching the plunger of the tension balancer to the thread at a pointafter it has passed through an adjustable tension regulator on thesewing machine,

moving the tension balancer away from the tension regulator, and

simultaneously adjusting the tension regulator in correlation with theindicia on the plunger until the appropriate tension is produced on thethread.

2. The method of claim 1, where the appropriate tension force isadjusted to be not less than 59 grams nor more than l62.5 grams.

3. A method of adjusting a sewing machine to produce an optimum stitchby the use of a calibrated tension balancer having a resiliently biasplunger with indicia comprising the steps of:

a. attaching the plunger of the tension balancer to the needle thread ata point on the thread after it has passed effectively beyond theadjustable needle thread tension regulator on the sewing machine,

b. moving the tension balancer away from the needle thread tension reulator, c. ad usting e needle thread tension regulator in correlationwith the indicia on the plunger until the appropriate tension isproduced on the needle thread,

d. removing the needle thread from the plunger and attaching the plungerto the bobbin thread after it has passed effectively beyond the bobbintension regulator on the sewing machine,

e. moving the tension balancer away from the bobbin, and

f. adjusting the bobbin tension regulator in correlation with theindicia on the plunger until the appropriate tension is produced on thebobbin thread.

4. The method of claim 3, where the needle thread tension force isadjusted to be approximately 83 grams greater than the bobbin threadtension force.

5. The method of claim 4, where the needle thread tension force isapproximately l52.5 grams.

1. A method of tensioning a threAd on a sewing machine by the use of acalibrated tension balancer having a resiliently bias plunger withindicia comprising the steps of: attaching the plunger of the tensionbalancer to the thread at a point after it has passed through anadjustable tension regulator on the sewing machine, moving the tensionbalancer away from the tension regulator, and simultaneously adjustingthe tension regulator in correlation with the indicia on the plungeruntil the appropriate tension is produced on the thread.
 2. The methodof claim 1, where the appropriate tension force is adjusted to be notless than 59 grams nor more than 162.5 grams.
 3. A method of adjusting asewing machine to produce an optimum stitch by the use of a calibratedtension balancer having a resiliently bias plunger with indiciacomprising the steps of: a. attaching the plunger of the tensionbalancer to the needle thread at a point on the thread after it haspassed effectively beyond the adjustable needle thread tension regulatoron the sewing machine, b. moving the tension balancer away from theneedle thread tension regulator, c. adjusting the needle thread tensionregulator in correlation with the indicia on the plunger until theappropriate tension is produced on the needle thread, d. removing theneedle thread from the plunger and attaching the plunger to the bobbinthread after it has passed effectively beyond the bobbin tensionregulator on the sewing machine, e. moving the tension balancer awayfrom the bobbin, and f. adjusting the bobbin tension regulator incorrelation with the indicia on the plunger until the appropriatetension is produced on the bobbin thread.
 4. The method of claim 3,where the needle thread tension force is adjusted to be approximately 83grams greater than the bobbin thread tension force.
 5. The method ofclaim 4, where the needle thread tension force is approximately 152.5grams.